There are a large number of techniques and apparatuses suited for positively locating an article and fixing the article in a particular position. In the general area of the machining, fabricating and welding of metals, there are a vast number of chucking, clamping and fixturing devices which are employed to locate and restrain a workpiece while various operations are performed.
These prior methods and apparatus include the vises, clamps, chucks and other similar embodiments and extend in complexity to the complex fixtures which are used to locate complex articles such as automobile engine components as successive machining and finishing operations are performed.
This invention was developed to solve a problem encountered in the inertia welding of large superalloy and titanium alloy disks to form a gas turbine engine structure known as a drum rotor. However, the invention is not limited to such applications.
The inertia welding process is by now a well known, well developed process described, for example, in U.S. Pat. Nos. 3,234,644, 3,235,162, 3,462,826, 3,591,068 and 4,365,136. The essence of an inertia welding process as it might be employed to bond two disks together is to hold one disk stationary, while rotating the other disk (usually with an attached flywheel). The rotating disk is forced against the stationary disk. The resultant frictional heat (resulting from the conversion of the kinetic energy to thermal energy) causes melting of the disks at the area where contact occurs. During the welding step, and especially at the end of the welding step, substantial axial pressure is applied to force the components together.
In the bonding of drum rotor disks made of nickel superalloys, where the bond area is about twenty square inches as much as 1,000,000 pounds of axial force is applied and the kinetic energy which is converted to heat is as much as 750,000 pound feet.
In the fabrication of a drum rotor, as many as eight or ten disks may be successively bonded together. A problem is encountered in such an operation in that the errors resulting from inertia welding machine misalignment, and deflection during bonding can combine to provide a finished article in which the axies of successive disks are not coincident. In a conventional inertia bonding machine, these errors are additive with the addition of each successive disk and in an 6 to 8 disk drum rotor the cumulative errors can be unacceptable.
In order to overcome this difficulty it was desired to have a workpiece locating system which could, in one condition, permit the workpiece to move laterally in a plane as much as plus or minus thirty thousandths of an inch. In another condition, the system fixedly locates the workpiece in the plane and relative to the inertia welding machine frame.